Enhanced Quantum Cutting via Li+ Doping from a Bi3+/Yb3+-Codoped Gadolinium Tungstate Phosphor

The Bi 3+ /Yb 3+ -codoped gadolinium tungstate phosphor has been synthesized through a solid-state reaction method. The structural characterization reveals the crystalline nature of the phosphor. The Bi 3+ -doped phosphor emits visible radiation from the blue to red regions upon excitation with 330 and 355 nm. The addition of Yb 3+ to the Bi 3+ -doped phosphor reduces the emission intensity in the visible region and emits an intense near-infrared (NIR) photon centered at 976 nm through a quantum-cutting (QC) phenomenon. This is due to cooperative energy transfer (CET) from the 3 P 1 level of Bi 3+ to the 2 F 5/2 level of Yb 3+ . The presence of Li + ions in the Bi 3+ /Yb 3+ -codoped phosphor enhances the emission intensity in the NIR region up to by 3 times, whereas the emission intensity in the visible region is significantly reduced. The energy transfer (ET) from the Bi 3+ ions to the Yb 3+ ions is confirmed by lifetime measurements, and the lifetime for the 3 P 1 level of Bi 3+ decreases continuously with increasing Yb 3+ concentration. The ET efficiency (η ETE ) and corresponding QC efficiency (η QE ) are calculated and found to be 29% and 129%, respectively. The presence of Li + enhances the QC efficiency of the phosphor up to 43%. Thus, the Bi 3+ /Yb 3+ /Li + -codoped phosphor is a promising candidate to enhance the efficiency of a crystalline-silicon-based solar cell through spectral conversion.